alpha(1)-Antitrypsin (AAT) deficiency is a common but under-recognised condition. Since its first description by Laurell and Eriksson in 1963, significant advances have been made in understanding the genetics, physiology and pathophysiology of this condition. The intravenous administration of purified AAT to AAT-deficient individuals has been shown to confer biochemical efficacy by raising the serum AAT level above an epidemiologically established 'protective threshold' while preserving the biochemical properties and functional capacity of the protease inhibitor. Although the lack of a large randomised controlled trial to date has precluded the definitive demonstration of clinical efficacy of intravenous AAT augmentation therapy, substantial evidence supporting its use in AAT-deficient individuals with moderate airflow obstruction has accumulated. For example, both large observational studies comparing rates of forced expiratory volume decline among recipients of augmentation therapy versus non-recipients have shown slower rates of decline among augmentation therapy recipients, especially those with moderately severe airflow obstruction. Also, some evidence suggests that use of augmentation therapy confers an anti-inflammatory effect. For example, a web-based survey suggested that recipients of augmentation therapy experienced fewer respiratory infections than non-recipients. Despite its high cost, intravenous AAT augmentation therapy remains the only US FDA-approved treatment option for patients with AAT deficiency. Research into new and evolving treatments is currently underway.